Area-wide biological control of disease vectors and agents affecting wildlife.

Two examples of area-wide programmes, employing the sterile insect technique (SIT), which have eradicated a parasite and a disease vector common to domestic and wild animals are described. New World screwworm (NWS), Cochliomyia hominivorax, caused significant morbidity and mortality of livestock and wild mammals in tropical and subtropical areas of America before eradication was achieved in North America using the SIT and other components of an integrated pest management (IPM) programme. Movement of wild as well as domestic animals from an area which is infested with screwworm to a free area requires prophylactic treatment. Tsetse fly-borne trypanosomosis has an immense influence on the distribution of people and livestock in Africa. The immunotolerance of wildlife to the parasites is an important factor in maintaining some areas livestock free as wildlife refuges. Slaughter has ceased of wild hoofstock species considered to be disease reservoirs for control purposes. The SIT, combined with other IPM measures, has resulted in the eradication of the tsetse fly and trypanosomosis from Zanzibar. Other programmes in Africa are underway. Microbial 'biopesticides' have also been employed successfully against plant insect pests and some vectors of human disease. It seems likely that for the immediate future, wildlife may benefit from area-wide biological control programmes, intended mainly to protect humans and/or domestic animals.

Myiasis: the battle continues against screwworm infestation.

The New World screwworm fly (Cochliomyia hominivorax) caused myiasis extensively among livestock in Mexico and the southern third of the USA until eradication was achieved by repeatedly releasing sterile males of the species on a massive scale. The pest appeared in Libya in 1988, the first time it had become established outside the western hemisphere. Because of the threat of myiasis in animals and people, not only in Libya but also elsewhere in Africa and beyond, a concerted campaign of sterile male releases was mounted with strong international support, and the outbreak has been eliminated. Action is continuing against the pest in Central America.